[Exim] Bug: BSMTP does not respect '-f<>'

As far as I can tell, this must have been in all versions of exim so far.
The man page says,

              If the  spe­
              cial setting -f <> is used by an untrusted user, it
              does not affect the sender for the purposes of man­
              aging  the  Sender:  and From: headers, but it does
              have the effect of causing any  SMTP  transmissions
              to be sent out with

               MAIL FROM: <>

However, this does not work for BSMTP transports. A short look over
the source tells that the pipe and appendfile drivers don't even have
the code to recognize this. As a consequence, an untrusted user can
not use '-f<>' when the message goes out via BSMTP (as opposed to
SMTP); it will have the normal MAIL FROM <user@host> line. Bad for
autoresponders and stuff like that.

Olaf